1. When one cannot "get it up" and has Erectial Disfunction
2. When one cannot ejaculate, or has sterile sperm.
As Grandma explained how Grandpa was Nut Lagging, we all threw up all over her nig face.
When you bust a fat nut(s) so hard you feel like you have jet lag
Bro i nutted 5 times i have Nut-Lag